They don’t even mention what system is running on the TV in the background (or maybe I missed it). Probably not one, where you can code your own modules as easily as with MagicMirror2. Edit: Nevermind, it is an Android 5.0, but still no words about the software itself.

Hm, this is no real usecase for me. The mirror - at least for me - is a technical and modern way to replace old fashioned paper calendars / schedulers with some addons like weather forecast, traffic jams and public transport delays, without having to use the smartphone.
I don’t want to browse websites while brushing my teeth or view the latest news while taking a shower :)